Heart failure patients are more prone to DRPs due to different factors, like polypharmacy, comorbidity, and alteration in pharmacokinetic properties of HF patients, which result in impaired hepatic and renal blood flow . Identifying, resolving, and preventing DRPs prevents detrimental health outcomes. Therefore, the identification and prevention of DRP occurrences are crucial.
The prevalence of DRP was found to be 66.2% and the average number of DRPs per patient was 1.19 + 1.18, which was lower than the study conducted at JUMC (83.5%) and 2.6 + 1.8. The difference could be due to setting differences; our study was conducted in hospitalized patients, in which senior physicians and clinical pharmacists are available more frequently than in ambulatory settings . However, it is almost in line with studies conducted at TASH (65.5%)  and Gonder University Hospital (63.4%), or an average of 1.17 + 1.1 per patient . Moreover, a study done on hospitalized heart failure patients at JUMC in 2014 showed DRPs were about 91% . This difference from the current study could be due to CP intervention in current study.
The most common DRPs in our study were treatment effectiveness-related problems (55.48%) and the least was ADE occurrence (21.6%). Suboptimal drug treatment and untreated indications accounted for approximately 28% and 25% of treatment effectiveness issues, respectively. In contrast to this, a study conducted at the ambulatory clinic of JUMC in 2018 showed that treatment effectiveness was about 83%, of which suboptimal drug therapy and untreated indications were about 55% and 27%, respectively . In addition to this, a study done in Barcelona showed that suboptimal drug therapy (31%) and the probability of ADE occurrence (16%) were comparable with our study . Whereas, a study conducted at TASH showed that treatment effectiveness-related problems (39%) were lower than our findings . Furthermore, a study done in the USA on outpatient heart failure showed that treatment effectiveness-related problems were about 36.8% . The discrepancy could be due to differences in the study design and settings, clinical characteristics, population demographics, medication therapy used, methods of DRP identification and classification, or sample size difference. Non-compliance was about 9%, which was in line with studies done on ambulatory HF patients in JUMC (9%) and Barcelona, Spain (14%) [11, 22]. However, a study done at TASH showed that non-compliance was about 45% . This could be due to differences in compliance assessment methods.
In our study, one-third of DRP causes were inappropriate drug selection and about 21% were dose selection-related problems. The new indication was about 60% of the causes of inappropriate drug selection, which was comparable with a study done at GUH which showed inappropriate drug selection and new indications were about 36% and 59%, respectively . On the other hand, inappropriate drug selection (34% and dose selection, 27%), carried out at tertiary care teaching hospitals in southern India, was comparable with our findings . However, a study on the general medical conditions of admitted geriatric patients at JUMC in 2017 showed that inappropriate drug selection was about 54% and the main causes of it were about 36% . This may be due to different medical conditions and only the geriatric population.
Different classes of drugs were involved in DRPs among heart failure patients admitted to a medical ward. In the present study, the most common classes of drugs implicated in DRPs were BBs (35%) and ACEIs (25.3%), which was consistent with a study at the ambulatory clinic of JUMC, where BBs and ACEIs were 34.4% and 24.8%, respectively . In addition to this, a study done in Taiwan showed that ACEI was about (21%) . Moreover, studies conducted at the ambulatory clinic of TASH and in hospitalized HF patients at JUMC showed that BBs, ACEIs, and antithrombotics were the most commonly implicated drug classes in DRPs, likewise our findings [10, 21]. Finally, a study done on the detection and management of medication errors in internal wards at a teaching hospital in Iran revealed that cardiovascular medications were the class with the highest detected errors (31.6%) by clinical pharmacists .
The result of multivariate logistic regression showed that khat chewers, comorbidity, prolonged hospital stay, and polypharmacy were independent predictors of DRPs. According to the current study, patients with a social history of chewing khat have an independent effect on DRPs. To our knowledge, there has been no study that supports our findings. Somehow, a study conducted in southern India found that patients having a social history of alcoholism do have independent predictors of DRPs . The plausible argument is that having a history of social drug use (chewing khat) may have contributed to patients' financial issues being disrupted. But still, more studies are needed to explicitly know the association between chewing khat and drug-related problems. In the current study, prolonged hospital stays were one of the independent predictors of DRPs among heart failure patients admitted to a medical ward. This was supported by studies done in Western Nepal and Pakistan  and the reason might be that the likelihood of getting multiple drugs increases with the increased length of hospital stay, which in turn will increase the likelihood of DRPs.
Comorbidity was another independent risk factor for DRPs in heart failure patients admitted to a medical ward. This is augmented by studies carried out at the ambulatory clinics of TASH and JUMC [10, 11, 29,30,31,32,33]. This could be due to patients with comorbidity being more likely to take more drugs to treat other diseases, causing disease-disease interaction, drug-drug interaction, and drug-disease interaction, which in turn makes patients more vulnerable to DRPs. Moreover, polypharmacy was also an independent predictor of DRPs, which was also supported by several studies [10, 11, 27, 30, 31, 34, 35]. This could be due to the fact that the more medications prescribed, the more drug-drug interactions, the risk of adverse events, difficulties with adherence, and the cost.
Clinical pharmacists' interventions in medical wards play a vital role in effectively identifying, resolving, and preventing DRPs. According to our study, clinical pharmacists' intervention acceptance rate was about 93%, of which about 81% of interventions were fully implemented and, from the outcome of the intervention, about 72% were solved. This result was comparable with studies carried out in Southern India and Karnataka, India, which revealed that clinical pharmacists' acceptance was about 97% and 96%, respectively [36, 37]. Moreover, a study carried out in Ghana, South Western Saudi Arabia, Northern Cyprus, and India showed that clinical pharmacists' intervention and acceptance rates were about two-thirds of the study population [38,39,40].